Considerable time and expense are utilized to free paved roads, airport runways and walks from ice in cold climates. Expendable materials which are destructive to pavements and machinery alike are used in large quantities, and when removed with the partially melted ice and snow, often require special dumping areas for various reasons. An example of one such material is the salt spread on many road surfaces which, when thrown up against wheel wells, metal flooring, frames and running gear of road vehicles, results in accelerated rust and thus greatly reduces the life of vehicles. Another example is the use of considerable quantities of urea on airport runways, requiring high acquisition, storage and disposal costs, and in addition resulting in very disagreeable odors when the ice melts.
Various schemes have been proposed to better solve this problem of ice removal which must be accomplished to allow the safe use of streets, highways, intersections, walks and airport runways. Proposals include that of Mouatt, U.S. Pat. No. 3,964,183, in which he concentrates an intense beam of visible light onto the interface of a coating of ice, snow or frost and the top surface of a pavement adequate to raise the temperature of the interfacial zone to the melting point of water so as to free the icy coating from the pavement and then quickly remove the ice, so freed, by other apparatus before it re-freezes. As inventor Mouatt notes, infra-red radiation has also been used in an attempt to remove ice from pavements. Mechanical means used alone, as he infers, fail to completely clean the surface of ice because of the adhesive forces between ice and other common materials, which forces exceed the internal cohesive strength of ice itself. The infra-red radiation method failed because of the need to supply the heat of fusion to the entire thickness of ice, coupled with the insulating effect of the standing water so formed above the remaining thickness of ice.
In a different field, micro-wave energy is proposed for use in U.S. Pat. No. 3,443,051 to Puschner to develop thermal wedge forms in rock to split the rock. Inventor Stone in U.S. Pat. No. 3,601,448 uses two micro-wave generators, spaced apart from one another and directed at concrete or rock, to produce spaced heat zones to expand the material so as to place high tensile forces on the unheated material between the heat patterns. In U.S. Pat. No. 4,175,885, inventor Jeppson discloses a method of producing a composite pavement in which a 915 M-Hz micro-wave generator and wave guide are passed very slowly over a cement concrete pavement, with the additional use of hot gas to heat the concrete to the depth of about 6 inches, so as to drive off moisture and use the hot concrete to lower the viscosity of a thermoplastic sealer for maximum penetration of sealer into the interstices of the concrete. However, the surface of concrete can be damaged by spalling when heat is applied.